SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK CORR 1 NWS STORM PREDICTION CENTER NORMAN OK 0110 AM CDT TUE APR 16 2013 VALID 161200Z - 171200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN PLAINS TO THE OH/TN VALLEYS... CORRECTED FOR WORDING ...SYNOPSIS... GRADUAL LARGE SCALE PATTERN AMPLIFICATION WILL CONTINUE TO OCCUR THROUGH THE PERIOD...HIGHLIGHTED BY AN INCREASINGLY PROMINENT WESTERN STATES LONGWAVE TROUGH AND PHASING POLAR/SUBTROPICAL JETS OVER THE SOUTHWEST DESERTS/FAR NORTHERN MEXICO INTO TONIGHT. TSTM POTENTIAL /INCLUDING SOME SEVERE/ WILL GENERALLY BE FOCUSED ALONG AN EAST-SOUTHEASTWARD MOVING COLD FRONT ACROSS THE OH VALLEY...WITH A SLOW-MOVING/STALLED PORTION OF THE FRONT EXTENDING SOUTHWESTWARD ACROSS THE OZARKS INTO THE SOUTHERN HIGH PLAINS INCLUDING NORTHWEST TX. ...MIDDLE MS AND OH/TN RIVER VALLEYS... SCATTERED CONVECTION WILL BE ONGOING THIS MORNING ALONG/IMMEDIATELY NORTH OF A COLD FRONT ACROSS THE MIDDLE MS VALLEY/MIDWEST. RELATIVELY LITTLE IF ANY SEVERE POTENTIAL IS EXPECTED DURING THE MORNING HOURS...BUT TSTMS SHOULD DIURNALLY INTENSIFY ALONG THE COLD FRONT AS IT CONTINUES A SLOW BUT STEADY EAST-SOUTHEASTWARD PROGRESSION THIS AFTERNOON ACROSS THE OH VALLEY. AROUND 60/LOWER 60S F SURFACE DEWPOINTS WILL BECOME INCREASINGLY PREVALENT WITHIN THE WARM SECTOR...WITH MODERATE INSTABILITY/WEAK INHIBITION EXPECTED BY EARLY/MID AFTERNOON. IN SPITE OF MID-LEVEL HEIGHT RISES...MODERATE SHEAR WILL COINCIDE WITH THE FRONTAL ZONE...SUCH THAT SEMI-ORGANIZED/SUSTAINED TSTMS ARE EXPECTED. CONVECTIVE LIKELIHOOD/CONFIDENCE IS NOT PARTICULARLY HIGH FARTHER SOUTH ACROSS THE TN VALLEY...BUT AT LEAST ISOLATED SEVERE TSTMS MAY BE POSSIBLE...PERHAPS AIDED BY A MID/HIGH LEVEL JET STREAK AND/OR WEAK LOW LEVEL CONFLUENCE. IN ALL...ISOLATED BOUTS OF DAMAGING WIND MAY BE THE PRIMARY RISK ACROSS THE REGION...WITH MARGINALLY SEVERE HAIL POSSIBLE AS WELL. ...SOUTHERN HIGH PLAINS LATE AFTERNOON/EARLY EVENING... BACKGROUND FORCING FOR ASCENT WILL BE WEAK AT BEST WITH NEAR-NEUTRAL HEIGHT TENDENCIES THROUGH PEAK HEATING. EVEN SO...AMPLE HEATING SHOULD OCCUR ACROSS THE SOUTHERN HIGH PLAINS INCLUDING PORTIONS OF WEST/NORTHWEST TX...WITH AT LEAST MODEST MASS CONVERGENCE NEAR A LOOSE ARCING FRONTAL BOUNDARY/WEAK SURFACE LOW/DRYLINE INDUCED TRIPLE POINT. ALONG WITH A RELATIVELY MOIST AIRMASS /LOWER 60S F SURFACE DEWPOINTS/...THESE FACTORS SHOULD BE SUFFICIENT FOR ISOLATED/WIDELY SCATTERED TSTM DEVELOPMENT LATE THIS AFTERNOON/EARLY EVENING...MOST PROBABLE ACROSS THE LOW ROLLING PLAINS OF TX. IF/WHERE STORMS DO DEVELOP THROUGH LATE AFTERNOON/EARLY EVENING...VEERING WIND PROFILES/40+ MID-LEVEL SOUTHWESTERLIES WILL BE MORE THAN ADEQUATE FOR A FEW SUSTAINED SUPERCELLS GIVEN THE DEGREE OF INSTABILITY /2000+ J PER KG MLCAPE/. LARGE HAIL WILL BE THE PRIMARY HAZARD...BUT SOME TORNADO THREAT MIGHT EXIST AS WELL IMMEDIATELY NEAR THE TRIPLE POINT/ARCING SYNOPTIC FRONTAL BOUNDARY. ...SOUTH-CENTRAL PLAINS TO LOWER MO VALLEY/MIDWEST TONIGHT... ALTHOUGH SPATIAL VARIABILITY IS CONSIDERABLE WITH RESPECT TO SHORT-TERM NUMERICAL GUIDANCE DETAILS...IT DOES SEEM LIKELY THAT STORMS WILL NOCTURNALLY INCREASE AND EXPAND EAST-NORTHEASTWARD ACROSS THE SOUTH-CENTRAL PLAINS TO THE OZARKS/LOWER MO VALLEY TONIGHT...POTENTIALLY INCLUDING PORTIONS OF NORTH OK INTO KS/MO AND ADJACENT IA/IL. THIS WILL BE AS A SOUTH-SOUTHWESTERLY LOW LEVEL JET STRENGTHENS/VEERS...WITH ASSOCIATED WARM/MOIST ADVECTION ABOVE A SHALLOW COOL/STABLE LAYER. THE COMBINATION OF MODERATE ELEVATED INSTABILITY/STRONG EFFECTIVE SHEAR WILL BE FAVORABLE FOR BOUTS OF LARGE HAIL INTO THE OVERNIGHT HOURS. WHILE GUIDANCE VARIABILITY /UNCERTAIN SPATIAL DETAILS/ PRECLUDES SUCH AT THIS TIME...HIGHER PROBABILITIES /SUCH AS A 30 PERCENT HAIL AND-OR SIG HAIL/ MAY ULTIMATELY BE WARRANTED. ..GUYER.. 04/16/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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